In an atomic power plant, spent fuels, which are taken out from a reactor core after an atomic power reactor has been operated for a certain period of time, are conventionally accommodated and stored in a spent fuel storage rack installed in a fuel storage pool, until a reprocessing is performed. In the spent fuel storage rack, the spent fuels are cooled for removing a decay heat thereof. In recent years, it has been required to increase a storage capacity of spent fuels by effectively utilizing a space in the fuel storage pool. In order to cope with this requirement, a distance between the stored spent fuels is narrowed, while a non-critical state between the fuels is maintained by interposing a material having a neutron absorption ability between the stored spent fuels. The interposed member also serves as a reinforcing member that supports the stored spent fuels, when an earthquake occurs. In this manner, there has been proposed a spent fuel storage rack capable of increasing a denseness.
As such a spent fuel storage rack, there has been known a spent fuel storage rack of a so-called lattice-like cell structure in which boron-added stainless steel plates, which are excellent in neutron absorption ability and in structural strength, are interposed one by one between stored spent fuels (for example, JP2000-258538A).
However, the boron-added stainless steel has a following disadvantageous feature. Namely, as an amount of added boron increases, a welding operation is more likely to impair a material strength of the boron-added stainless steel. Thus, when lattice plate members using the boron-added stainless steel are integrated by welding to form a lattice plate, an amount of boron to be added is limited, which limits an ability to absorb neutrons.
Further, when lattice plate members are integrated by welding to form a lattice plate, the welding operation is complicated, because lattice-like cells are adjacent to each other. Furthermore, since the welding operation has to be performed in the narrow lattice-like cells, it is necessary to use a special jig, which is economically disadvantageous.